The present invention relates generally to converters for direct-to-home (DTH) satellite broadcast television systems, and more particularly to a converter for a DTH satellite broadcast television system for receiving C-band broadcasts.
Currently, about 4 million households in the United States employ a large television receive only (TVRO) satellite dish antenna for receiving C-Band television broadcast programming. These antennae receive transmissions in analog format from a constellation of C-Band geosynchronous satellites, which relay television programs from groundstations to the TVRO dish antennas. The existing C-Band broadcasting systems employ a converter (or receiver) located near the television to output a television channel specified by the viewer to a television or video cassette recorder (VCR). The converter is connected to the TVRO dish via a long coaxial cable that rum from the converter to the equipment (termed the outdoor unit) mounted outside near the TVRO dish. The coaxial cable may in addition be assembled with other cables and signals, at least one of which carries a control signal to the antenna to select the polarization of the RF signals, since the RF signals transmitted from the satellite are either vertically or horizontally polarized. The coaxial cable may also be assembled with a cable that carries a control signal to the antenna to steer the antenna from inside the house. Since these TVRO dishes are large, automatic steering is often used to avoid the inconvenience of climbing on the roof and resteering the antenna if broadcasts from a different satellite are desired.
While digital technology has been in use in telecommunications for some time, its use has been mostly limited to voice and data applications, until recently. Converting voice-grade signals into a digital format was relatively easy, but the task of digitizing video signals efficiently presented a much greater technological challenge.
Video signals that are digitized but not compressed require high bit rates. Consequently, they use the same amount or more of RF spectrum bandwidth as the analog formats they were attempting to replace. While other benefits would ensue from simply converting analog video signals to digital video signals, such as improved quality, the resulting increase in bandwidth and power from this conversion would increase satellite costs dramatically.
The advent of digital chip technology and sophisticated video data compression algorithms makes it possible for broadcasters to squeeze a digital video signal into far less spectrum bandwidth. Multiple video signals that were compressed using these data compression algorithms can now fit into the bandwidth reserved for a single analog video signal. Thus, the cost of satellite distribution decreases because less bandwidth is required for each video feed. Consequently, digital television is or soon will be available to the public. Unfortunately for the owners of the large TVRO satellite antennas, the advent of digital television may make their TVRO dishes obsolete, i.e., they must now buy new antennas and systems for receiving the new digital television, which is currently being broadcast at frequencies different from that for which these TVRO antennas are designed. The owners of these dish antennas invested upwards of $2500 in their systems, and are less likely to reinvest a similar amount in a new system. Therefore, a transition from analog TV to digital TV will prove to be an expensive proposition for these TVRO dish owners.
The present invention is therefore directed to the problem of developing a converter for use in a direct broadcast television system that will allow simultaneous reception of new digital C-band television and the current analog television signals, without requiring a major investment by the current users of analog television received via TVRO satellite antennas. The present invention is therefore directed to the problem of developing a dual converter that will receive both analog and digital TV so that a smooth and inexpensive transition from analog to digital TV is possible. Furthermore, the present invention is directed to the problem of providing a converter that provides complete flexibility to the broadcast system operator when assigning satellite resources, yet will provide a smooth transition from analog C-Band television to digital C-Band television.